Haha, nowadays that’s nearly a philosophical question!
I guess most people in architecture and design use Grasshopper for experimentation - to come up with fancy, novel shapes -, or to make repetitive tasks, - like doing the same or similar things over and over - faster and simpler.
The possibilities seem nearly endless, although the app itself is limited by its performance and the power of the machine it runs on.
Check out YouTube or other social media platforms to see what folks are up to, and don’t be discouraged by many architectural designers only using it for lame facade/shell concepts. The possibilities go far beyond that!
Kangaroo is a** physics engine** that it a part of Grasshopper, since Rhino 6 at least. It’s primarily used for interactive simulation, form-finding, optimisation of meshes, etc. but again the possibilities are quite manifold. I’d say check out Daniel Piker’s Vimeo, where he showcases many examples of what his baby (he’s the inventor/developer) is capable of.
In my opinion, most creative people - not only in the sense of “artists”, but folks that create/design/make things, objects, stuff - can profit from using Grasshopper.
It’s up to you individually to find out what you want to utilise it for, and whether you want to invest the time necessary to learn the tool!